With respect to the aforementioned application, previously known methods of fixing flexible sheeting to a framework have involved forming a hem around the perimeter of the sheeting and fastening the hem to the framework by means of nailed battens or by the use of dowels and twine. With regard to the latter, wooden dowels are passed through the hem at spaced apart locations and twine is firstly laced through the dowels and subsequently fixed to the frame work by means of staples. Both of these methods have the disadvantages. In the case of nailed battens, the sheeting has a tendency to tear, and the battens have a tendency to work away from the framework, particularly in windy conditions. In the case of dowels and twine, tensile forces within the sheeting, over a period of time, have a tendency to stress the lacing and eventually cause the staples to pull out, thereby releasing the sheeting. Additionally, the sheeting material often times tears through the dowels when subjected to extremely large transient tensile forces such as do arise in windy conditions, causing not only the release of the sheeting but also damage to the sheeting.
In order to overcome the disadvantages of the aforementioned methods of fastening sheeting, several products have been proposed which utilize a channel member and a mating wedge or clip member, which are capable of being deformedly interconnected to form a joint. In these arrangements, one member is fixedly mounted to the greenhouse or cloche framework, and the sheeting is clamped to this member by disposing it between the respective members of the joint prior to interconnection and subsequently pressing the other member into engagement with the fixed member so as to clamp or pin the sheeting between the members. Examples of this type of fastening are disclosed in prior patent specification numbers AU-43065/68, DE-2433638, AU-33920/84, AU-38379/85 and BE-98594.
Each of the prior art fastening devices disclosed in these specifications relies upon the fixing of the channel member, usually formed of aluminium, to the framework which supports the sheeting. The sheeting is then anchored by pushing the wedge or clip, usually formed o plastic material, into the channel with the sheeting interposed between the channel and the clip. Consequently, the channel member and/or clip is required to be deformed to subsequently allow frictional engagement between the members and thus the formation of the joint.
The types of frictional fastening suffer from several disadvantages as a result of their intrinsic design. Moreover, these types of fastening for their fastening ability rely upon the frictional force created between the interconnected members being greater than any tensile or tensioning force applied to the sheeting, such that these forces are in direct opposition to each other. It has been found, however, that in gusty wind conditions where relatively large and repetitive tensile forces are applied to the sheeting material, the wedge or clip members have a tendency to be forced apart due to the tensile forces on the sheeting providing a generally transverse force component within the confines of the channel, directly against the wedge or clip member, due to the sheeting material in the vicinity of the channel being displaced from the general plane of the sheeting which is actually subjected to the tensile forces. Furthermore, due to these devices relying upon deformation of either or both the channel member and wedge or clip member, such a type of fastening is not conducive to repeated usage on the same portion of sheeting, since the sheeting material in the vicinity of the channel is subjected to a relatively high degree of stress during the interconnecting operation. Thus repeated release and re-application of the fastening would have a tendency to cause severe wear of that portion of the sheeting retained within the joint. Additionally, the release of the joint would be a relatively difficult operation since the application of a force greater than the frictional force maintaining the joint, would need to be applied to the wedge or clip member in order to ensure its release.